#include <iostream>
#include <string>
#include <cstdlib>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

// Fater process -> read
// Child process -> write
int main()
{
    // 1. 创建管道
    int fds[2] = {0};
    int n = pipe(fds); // fds:输出型参数
    if (n != 0)
    {
        std::cerr << "pipe error" << std::endl;
        return 1;
    }

    // Fater process -> read
    // Child process -> write
    // 2. 创建子进程
    pid_t id = fork();
    if (id < 0)
    {
        std::cerr << "fork error" << std::endl;
        return 2;
    }
    else if (id == 0)
    {
        // 子进程
        // 3. 关闭不需要的fd,关闭read
        close(fds[0]);

        int cnt = 0;
        int total = 0;
        while (true)
        {
            std::string message = "h";
            // message += std::to_string(getpid());
            // message += ", ";
            // message += std::to_string(cnt);

            // fds[1]
            total += ::write(fds[1], message.c_str(), message.size());
            cnt++;
            std::cout << "total: " << total << std::endl;
            sleep(2);

            // break;
        }

        exit(0);
    }
    else
    {
        // 父进程
        // 3. 关闭不需要的fd，关闭write
        close(fds[1]);

        char buffer[1024];
        while (true)
        {
            sleep(1);
            ssize_t n = ::read(fds[0], buffer, 1024);
            if (n > 0)
            {
                buffer[n] = 0;
                std::cout << "child->father, message: " << buffer << std::endl;
            }
            else if(n == 0) 
            {
                // 如果写端关闭
                // 读端读完管道内部的数据，在读取的时候，
                // 就会读取到返回值0，表示对端关闭，也表示读到文件结尾
                std::cout << "n:" << n << std::endl;
                std::cout << "child quit ??? me too" << std::endl;
                break;
            }
            close(fds[0]);
            break;
            std::cout << std::endl;
        }

        int status = 0;
        pid_t rid = waitpid(id, &status, 0);
        std::cout << "father wait child success: " << rid << " exit code: " <<
             ((status<<8)&0xFF) << ", exit sig: " << (status & 0x7F) << std::endl;
    }

    return 0;
}